This invention relates generally to soldering devices. More particularly, the present invention relates to an improved solder tip and method of soldering which results in consistently reliable solder joints. The apparatus of the present invention is particularly advantageous for use in intricate soldering operations for example such as hooking up magnetic head wires to solder pads in magnetic disk drives.
Soldering techniques have long been used to connect wires or conductive leads to terminal pads. There are a variety of soldering devices and techniques which are used to form solder connections. In the simplest form, solder connections are made by using a manual soldering iron to heat solder in conjunction with flux. In this instance, solder is fed to the joint by hand. More sophisticated systems are used, at greater expense, to provide solder connections which are more reliable than those yielded by conventional hand soldering techniques. A common technique referred to as reflow soldering involves the use of preformed deposits of solder placed close to the joint before heating. Heating the solder causes it to reflow, allowing immersion of a wire in the molten solder.
With any approach, the increasing trend toward micro-miniaturization and high density packaging in the electronics and other manufacturing industries has made the task of soldering more difficult. Often, conductive leads are finer than a human hair, making it difficult to form a reliable solder joint.
Moreover, connections are ordinarily placed in such close proximity that bridging or short circuit problems tend to occur more easily. Further, because of the site of the solder joint and the resulting difficulty in making the solder connection, the joint is often very weak or has a troublesome tail end extending therefrom, which increases the probability of a short circuit. Inadequate clearance for the operation of any severing mechanism makes it difficult to remove such tail ends. This problem is particularly significant where many leads are located within a small space. Tail ends commonly are manually removed subsequent to the soldering operation by cutting the tail end with some sort of severing mechanism.
A further drawback when the solder and flux are applied manually is that the heating of flux generally results in a generation of fumes and/or smoke which are usually objectionable to the solderer. Even with the use of conventional exhaust hoods, the flux fumes rise from the soldering site and pass by the operator before being withdrawn by an exhaust system. Fumes and smoke obstruct the soldering operator's vision and make it more difficult for him or her to observe the fine conductive leads and the soldering operation. Moreover, expanding gases generated during the soldering operation result in a pressure build up which causes the solder to squeeze out around the solder pad. This is an area of grave concern especially if the solder which has squeezed out comes in contact with an adjacent solder pad. Normally, a certain amount of clearance between adjacent pads is always maintained. Thus, loose solder is a significant problem and has to be removed.
The segment of wire to be soldered is commonly prestripped either manually or by any other technique prior to initiating a soldering operation. Obviating the insulation stripping operation, which is normally required, is desirable in any application, in particular, where a large number of leads are soldered. In an attempt to eliminate the insulation stripping operation, the wire is subjected to extremely high temperatures sufficient to automatically break the insulation from the wire. However, subjecting the wire to extremely high temperatures is not always desirable because high temperatures are more likely to damage the areas in the immediate vicinity.
In particular, in the field of magnetic disk drives, when hooking up magnetic head wires to solder pads, the conductivity and the resistance provided by the wire are of paramount importance. In order to make a reliable connection, it is essential for the magnetic wire to be properly covered with solder. Additionally, in a reflow soldering system, the magnetic wire sometimes has a tendency to float to the top of the solder deposit which results in a weak connection. Conventionally used soldering tips also have a tendency to ruin the (KAPTON) layer on the Printed Circuit Board (PCB) and sometimes the adhesive squeeze-out around the solder pad.
The foregoing problems have created an ongoing quest and an urgent need for an improved soldering technique which is reliable and efficient yet economical.